Abrasive blasting apparatus



Aug. 14, 1962 M. E. FAHRNEY ETAL 3,048,947

ABRAsIvE BLASTING APPARATUS 5 Sheets-Sheet l Filed July 23. 1959 INVENTORS George POWSH 'i, j Maxwell EJFG Fung 55".; Y f' j ATTOI Allg 14, 1962 M. E. FAHRNEY ETAL. 3,048,947

ABRASIVE BLASTING APPARATUS 3 Sheets-Sheet 2 Filed July 23, 1959 INVENTORS George W. Powell Maxwell ETC: hmej BY j@ @mgm Aug. 14, 1962 M. E. FAHRNEY ETAL 3,048,947

ABRAsIvE BLASTING APPARATUS Filed July 23. 1959 5 Sheets-$heet 5 INVENTORA George W. Powell F- Maxwell E. Fuhme) 1mg!! $9 73 77 ATTORNEYS arent 3,048,947 Patented Aug. 14, 1962 3,048,947 ABRASIVE BLASTING APPARATUS Maxwell E. Fahrney and George W. Powell, Hagerstown, Md., assignors to Pangborn Corporation, Hagerstown, Md., a corporation of Maryland Filed .luly 23, 1959, Ser. No. 829,078 10 Claims. (Cl. 51-13) The present invention relates to apparatus for sub jecting work pieces to a blast of abrasive particles, and particularly to such apparatus in which the work pieces are tumbled in a trough-shaped conveyor to expose all their surfaces for such blasting.

Among the objects of the present invention is the provision of novel apparatus of the above kind `to enable efficient operation with fewer maintenance difficulties.

Further objects of the present invention include the provision of abrasive blasting apparatus which is more rugged, so that it is better suited for treating massive work pieces.

A still further object of the present invention is the construction of more versatile blasting apparatus and the resultant simplification of the manner in which work pieces can be treated.

The above, as well as additional objects of the present invention, will be more clearly understood from the following description of several of its exemplications, reference being made to the accompanying drawings wherein:

FIG. l is a partly broken away side View of one form of abrasive blasting apparatus illustrative of the present invention;

FIG. 2 is an enlarged sectional View of a portion of the apparatus of FIG. l, more clearly showing the con struction;

FIG. 3 is a detailed view of another portion of the apparatus of FIG. l with external structure removed;

FIG. 4 is a fragmentary sectional view of the construction of FIG. l taken along the line 4 4;

FIG. 5 is a fragmentary side view of the construction of FG. l, showing the apparatus in a different operating condition;

FIG. 6 is an enlarged sectional View of a still further portion of the apparatus of FIG. l;

FIG. 7 is a plan View of the part illustrated in FIG. 6; and

FIG. 8 is a view similar to FIG. 1, of a lmodified form of apparatus representative of the present invention.

One of the most significant problems in the abrasive blasting field is the installation of the apparatus. In-

asmuch as the apparatus is most widely used with products such as metal castings which are prepared by batch manufacturing techniques, a batch treatment type of apparatus as shown in U.S. Patent 2,533,265, granted December l2, 1950, is very desirable. Such an apparatus has a conveyor arranged to move through a path that forms a laterally tilted trough in which the work pieces are held and tumbled while they are blasted, and a housing around the conveyor keeps the blastant particles confined against escape into the surroundings. A doorway is provided through `which to load and unload the work pieces and by inclining the doorway so that it faces upA wardly above the conveyor, heavy work pieces can be loaded by an overhead crane if desired.

However, the door-way must Ibe very effectively sealed inasmuch as any escape of the flying particles of abrasive would render the surroundings hazardous to personnel.

In addition, the sealing should not unduly cucumber the equipment. For installation purposes, the entire equipment should be as compact as possible. Its front should be completely unobstructed to avoid restricting the loading. A good bit of both sides are occupied by the conveyor supporting mechanism, a significant portion of one side at least must be devoted to holding the equipments controls, blastant recovery and recirculation structure generally extends over a good bit of its external walls and suction apparatus and hoods for controlling dust generated by the equipment also occupies a substantial amount of those walls.

As a result, a good deal of mechanism must be mounted on the roof of the equipment. Included in this topmounted mechanism are one or more abrasive throwing wheels, drive mechanisms for the door and sometimes for the conveyor, abrasive feed hoppers and lines to supply blastant to the wheels, as well as abrasive supply control valves to stop the abrasive ow rapidly inasmuch as the wheels take a long time to stop and the extra time is otherwise wasted.

According to the present invention, apparatus of the above type has the upwardly inclined loading doorway provided with a sliding door and with a door track that extends along the inclined sides of the doorway and vertically upwardly from the top of the doorway, the door being a single rigid panel slidably fitted in the track, the track at its intermediate portion being free of structure that would keep the intermediate portion of the door from lifting out of the track, the door sides as well as the inclined section of the track `having cooperating labyrinth seal elements, and the upper portion of the door having securing elements cooperating with the upper portion of the inclined track section to cause the upper portion of the door to seal against the inclined track when the door is lowered.

The labyrinth seal can also include a rubber strip secured to one of the sealing surfaces and projecting out sufhciently far to be compressed by the cooperating sealing surface when in sealing position.

Referring now to the figures, FIGURE l shows the general combination of an abrasive blasting apparatus typical of the present invention. This apparatus includes a housing or cabinet 20 with side ywalls 21, Z2, a rear wall 24, and a roof 26. The front of the cabinet is open to provide a doorway generally indicated at 3f), that can be closed by a combination of an upper door 32 and a lower door 34.

Within the cabinet is mounted an endless conveyor 4t) shown as made of metal bars or slats 42 extending transversely across the width of the conveyor and connected together at their ends by chains that are looped around a pair of front guide sprockets 46 and a pair of rear drive sprockets 48. A set of guide or tension control sprockets or rollers 50 can also be provided to make sure the conveyor is held in place on the sprockets 46, 48, and to also help keep the opposing runs of the conveyor apart. A pair of sturdy guide discs 54 are rotatably mounted adjacent the inside surfaces of the side walls `and between the front and rear sprockets 46, 48 so as to provide convex guides that compel the upper flight S8 of the conveyor to follow a concave path 60. This concave path resembles a `trough which is laterally inclined so that it faces the upper portion of the doorway 39.

The conveyor is operated by an electric motor (not shown) mounted on the outer face of a side wall and connected as by way of a speed reducer (also `not shown) to the shaft 62 that carries the drive sprockets. For heavy Work, as for example, where the machine has a working capacity of 40 or more cubic feet, the slats or bars 42 of the conveyor are preferably made extremely resistant ot the blasting as well as to shock, and are also well reinforced. The slats can, for example, be as much as an inch-and-a-half in thickness, and can be provided with strengthening ribs welded on or bolted on to their back faces. A specific reinforced slat construc- P tion that has been found highly desirable is shown in greater detail in FIGURES 6r and 7.

The internal construction of the cabinet can in general be of standard form as shown, for example, in the above-identified U.S. Patent 2,533,265 or in U.S. Patent 2,716,310, granted August 30, 1955. As is usual with such machines, they have one or more throwing wheel assemblies mounted over the trough of the conveyor `on the roof 26, a slot in the roof providing a passageway for the abrasive particles to be thrown down into the trough. The abrasive particles are caused to drop through the conveyor, between the slats or through perforations in the slats, and are collected at or below the base of the apparatus from which they are moved laterally as by means of a vibrating pan conveyor 64 and carried to the bottom of an elevator conveyor 66 which lifts them to a suitable height alongside the cabinet. Here the lifted particles are delivered to a separator 68 which traps coarse particles, wires, etc., and the fines which are not reusable are separated and dischanged through the conduit 70. The reusable particles are returned to the wheel assembly 80 through hopper 82. Suction conduits 96, 98 are also provided to draw olf dust emitted in the operation of the machine and can ybe connected to a common manifold.

The doors 32, 34 are each of the slidable type inasmuch as slidable connections operate better and are more readily sealed against leakage of the particles. Upper door 32 is shown as an integral panel reinforced if desired by marginal flanges or angles 100, 101. AS shown more clearly in FIGURE 4, the side margins of upper door 32 extend somewhat beyond the side walls and carry rollers 106 that iit in a trackway 107 formed by plates 108, 110 and connecting web 112 secured to the side walls and also projecting outwardly therefrom. A wear plate 114 is shown as fastened in the trackway to provide a wear-resistant surface for engagement by the rollers 106.

Between the trackway and the side wall 22, a labyrinthine sealing arrangement is built up by bars 116, 118 secured to plate 108 and projecting towards the door panel, along with an intervening bar 120 secured to the door panel and projecting toward plate 108. Additional labyrinthine elements can be provided as shown by the bars 122, 124, so that the passage of particles from the blasting compartment is sharply restricted. A wear plate 128 can also be provided on the inside surface of side wall 22 to cooperate with bars 122 and 124 in further improving the sealing action as shown.

Best results are obtained when at least one of the bars that form the labyrinthine passageway is made of rubber or similar resilient material that is actually brought in firm engagement with both the door panel and the plate 108. Such a rubber bar not only establishes good sealing engagement, but, in addition, the sliding action of the door panel causes the rubber bar to wipe clear lche sealing site and thereby assure good sealing every time.

Above the doorway 30 the trackway 107 extends up vertical-ly as shown at 132 so as to avoid obstructing the roof of the cabinet. The vertical trackway section can also be extended to provide a mounting for pulleys 134 that can be used for opening and closing the door. In the illustrated embodiment, cables 136 connected to flanges 138 projecting outwardly on the door 32, are guided over pulleys 134 and wound up on drum stubs 140 mounted on either side of hopper 82. One or more electric motors can be used to operate the drums. A suitably located switch controls the actuation of the drums, and causes them to rotate in one direction to wind in the cables thereby lifting the door, and when desired causing them to rotate in the opposite direction to unwind the cables thereby lowering the door.

The closed position of the door is illustrated in FIG. 1. As thedoor is lifted open its upper rollers reach the verticaltrackway section and further upward travel causes the intermediate portion of the door to be lifted away from the adjacent portions of the trackway. This opens up the labyrinthine side seals and disengages rubber bar 120 from plate 108, except at the lowermost edge of the door panel. The upper trackway section 132 need have no side sealing structure. In FIG. 5, the door 32 is shown by dash-dot lines in its partly open position, and by full lines in its fully open position.

lt has been found particularly advantageous to have the top of the door, when closed, pressed rmly against the doorway inasmuch as this greatly improves the sealing section. For this purpose, as illustrated more clearly in FlG. 3 the door carries at its upper edge a ange 144 upon which rollers 146 are mounted `for coaction with cams 148 positioned on the roof 26. These rollers do not engage the cams when the door is open, but when it is being closed, the rollers reach the cam surface just before the door is completely lowered, and the remainder of the downward travel causes the rollers to move in ou the cams and thereby draw the door top iirmly against the doorway edge. This brings the upper portions of the rubber bar 120 into very effective sealing engagement.

Another feature of the present invention is the provision of a baffle, as indicated at carried on the internal side of the door 32 and extending toward the adjacent portion of the conveyor 40. This baffle can be made of metal or other sturdy material spaced slightly from the conveyor and prevents tumbling work pieces from falling over the front edge of the conveyor.

A suitable spacing between the baffle and conveyor, can be 2 inches or somewhat less. Such a bale running across the entire width of the door also sharply reduces the number and velocity of any particles that reach the lower door 34, and no side seals need therefore be provided in the lower portion of the doorway. This portion of the doorway faces downwardly so that opening of the lower door 34 opens a space under the front of the conveyor and permits unloading of work pieces by merely reversing the conveyor travel in the conventional way.

Door 34 is shown in greater detail in FIG. 2 as having a pliable panel 166 of a material such as rubber, extending around the doorway portion that is curved to join the oppositely sloping top and bottom sections. Panel 166 is secured to a rigid extension panel 16S which only travels along the uncurved portion of the doorway and is in turn connected (FIG. 1) by actuating link 170 and bell crank 172 to an actuator such as a pneumatic cylinder (not shown). Rollers held on the side edges of the panels 166, 168 guide the panels in trackways that can be extensions of the upper trackways 107. For attachment to the pliable panel, the rollers can be carried by bars 182 whose ends are bent back on themselves to clamp them to the panel. The bars preferably extend as stiffening supports over the entire width of the pliable panel to keep it from falling out of the trackways.

The conveyor slats 42 are more clearly illustrated by FIGS. 6 and 7 where only one slat is shown. This slat has an elongated body portion 71 at each end of which is secured a connecting support 72 that includes a length 73 overlapping the slat ends and an offset arm 74 with securing means such as bolt-receiving holes 75 for connecting the slat body to a chain. In this way chains at both ends of `a series of slats connect the series together to make the conveyor.

For the larger sizes of conveyors, used to tumble the most `massive work pieces, it is essential that the slats have a long life. The cost of replacement is otherwise prohibitive. In accordance with the present invention, long life is contributed by specially reeinforcing the slats as illustrated. To the back face of each slat is secured as by welding a strengthening rib 76. This rib extends along the length of the slat and overlaps with the connector lengths 73. To accomplish this, the connector lengths 73 `are slotted at the inner ends of their overlap, as illustrated at 77, and the ribs 76 project into the slots. In addition a stilener bar 78 is secured to the bottom of the rib 76, again as by welding, and extends along substantially the entire length of the rib.

The slat bodies 71 are made replaceable, as by having them bol-ted to the connector supports 72 in the manner illustrated in FIGS. 6 and 7. Where it is desired to further save the replacement costs, the bodies 71 can be faced with wear plates 79, also bolted in place and merely of uniform llat construction so as to be relatively inexpensive. It is helpful to have the slat bodies provided with perforations as indicated at 81 to help the blastant particles fall through the conveyor and into the recirculation system. Such openings `would of course extend through the slat body and the wear plate. When a readily detachable plate is used, the slats can, if desired, be permanently secured to the connector supports 72, as by welding, inasmuch as the slat bodies need never be disassembled from their connector supports.

Although the slats can be made suiiciently sturdy without the elaborate reenforcement described above, in use the surface of the slat body is gradually worn away so that without this reenforcement, replacement is much more frequent. By way of example, the slat body can have a thickness of as much as 11/2 inches, and even with a strengthening rib in the form of a bar 2 inches wide and 3 inches high, it can be made to go through many more hours `of operation with the overlap between the rib and the connection supports, and with the stiffener bar 78. In such a combination with the stiffener bar in the form of another 2 inch by 3 inch bar, the slats will have a useful life of many thousands of operating hours before any maintenance is needed, and the only maintennace then required is generally a replacement of lthe wear plate. A ywear plate thickness of only 1/2 inch is desirable since during this life the loss of metal is generally less than this amount. In other words, the body of the slat can have a top member in the 'form of a l inch thick plate bolted to a 1/2 inch thick wear plate, and strengthened with the above described 2 inch by 3 inch rib and stiffener.

For the above use the overlap of the rib with the connector supports should extend longitudinally of the slat a distance suicient to enable secure anchorage of the connector supports lalong side the overlap. Where this anchorage is elected by bolting as at 80, at least one pair of bolts should be located as far apart as possible longitudinally within the overlap. A minimum of several inches between bolt holes 3() is then needed. The total overlap distance can range from about 4 to about 8 inches. As illustrated, a pair of such bolt holes 80 can be provided on each connector length 73 both sides of the slot 77. This construction is sufciently strong even though the stiffener bar 78 terminates before it reaches the overlaps, although the stiiener bar can if desired be extended into the overlaps.

The slats can be arranged in any desired relation with each other, and the construction of FIG. 1 has them arranged so that one long edge of one slat overlies the adjacent edge of the next slat to thereby reduce the possibility of having work pieces pinched between the slats. For the overlying construction the slat bodies are tilted somewhat with respect to the path through which they are carried by the conveyor chains and the connector supporters 72 can then be twisted in shape, as more clearly shown in FIG. 6, in order to effect the tilt.

Although the slat of FIGS. 6 and 7 are secured by connecting supports that are in turn fastened to the chains as by bolting, these supports may also be integral portions of the chains as by casting them in the form of integral later al extensions on the individual links of the chain.

FIG. 8 illustrates a modification of the invention in which a blasting machine is used not only to blast castings, but also to shake out cores, wires, sand, etc., from the castings and thereby simplify their treatment. Because the shaking-out operation makes a lot more work for the blastant recirculation system, the apparatus of FIG. 8 has a much larger separator section 200 than ordinarily used with its tumbling conveyor. The ordinary relationship of these two components is illustrated in FIG. l. The recirculation elevator 202 is also `made much larger, both in horizontal section so as to lift more materials, and in height to `carry this material to the top of the larger sized separator. The remainder of the apparatus of FIG. 8 can be generally similar to that of FIG. l.

It will be noted that in FIG. 8 the conveyor drive mechanism is represented by dash lines 20d as mounted on the outer surface of a side wall of the blasting compartment. An externally mounted hydraulic cylinder 266 is also shown here as connected to operate the lower door, and a take-up adjustment for the idler rollers or pulleys is also shown at 208. For maintenance purposes a ladder 210 can be mounted on one side of the housing.

Also, the construction of FIG. 8 can be mounted over a pit, as shown at 84 in FIG. 1, so as to provide a space for maintenance personnel to stand in, inspect and make any adjustments that might be needed in the lower portions of the housing.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed:

l. In an apparatus for tumbling a batch of work pieces in a trough-shaped conveyor enclosed in a housing having a loading and unloading doorway, and projecting a blast of abrasive particles against the tumbling `work pieces and at the same time keep the particles from leaking out through the doorway, the improvement according to which the upper portion of the doorway' is inclined position facing upwardly and has a sliding door with a door track that extends along the inclined sides of the doorway and vertically upwardly from the top of the doorway, the door being a single rigid panel slidably fitted in the track, the track at its intermediate portion being open to allow the intermediate portion of the door to lift out of the track, the door sides as well as the inclined section of the track having cooperating labyrinth seal elements, and the upper portion of the door having securing elements cooperat ing with the upper portion of the door to seal against the inclined track when the door is lowered.

2. The combination of claim 1 in which the labyrinth seal elements include a rubber strip secured to one of the sealing surfaces in a position in which it extends sufficiently far to be compressed by the cooperating sealing surface When in sealing position.

3. The combination of claim l in which the lower portion of the doorway is inclined to face downwardly and is provided with a second sliding door that cooperates with the irst sliding door to complete the closure for the doorway, and both doors are connected for substantially simultaneous operation.

4. In an apparatus for tumbling a batch of work pieces in a trough-shaped conveyor enclosed in a housing having a loading and unloading doorway, and projecting a blast of abrasive particles against the tumbling work pieces and at the same time keep the particles from leaking out through the doorway, the improvement according to which the upper portion of the doorway is in inclined position facing upwardly and has a sliding door with a door track that extends along the inclined sides of the doorway and vertically upwardly from the top of the doorway, the door being a single rigid panel slidably iitted in the track, the track at its intermediate portion being open to allow the intermediate portion of the door to lift out of the track, the door sides as well as the inclined section of the track having cooperating labyrinth seal elements, and a bathe is carried on the inner surface of the panel extending inwardly of the housing and toward the conveyor to block the passage of work pieces into the space between the door and the conveyor.

5. A combined shake-out and blasting apparatus for castings, the apparatus having a trough-shaped conveyor for tumbling the castings, a housing enclosing the conveyor, blasting mechanism mounted on the upper portion of the housing for projecting blastant particles against castings in the conveyor trough, the housing preventing the escape of flying particles and including a loading and unloading doorway the upper portion of which is in inclined position facing upwardly, a one-piece slidingy door for said doorway portion, a door track carried by said doorway portion and correspondingly inclined, a track extension extending vertically up from the top of said doorway portion so as not to occupy the adjacent space over the top of the housing, a blastant separator mounted on top of the housing and occupying said adjacent space, and blastant recirculating structure mounted in the lower portion of the housing and alongside the housing to collect the particles as they drop in the housing and deliver the particles to the separator, said separator being connected to separate the shake-out particles from the blastant particles in the recirculated material and deliver the blastant particles to the blasting mechanism.

6. In a blasting apparatus having a trough-shaped conveyor in which massive work pieces are blasted with particles while they are tumbled, the improvement according to which the conveyor is made up of metal slats each having connector supports bolted on at each end, each support overlapping the slat end to which it is attached and being slotted longitudinally of the slat at the inner end of the overlap, only a single strengthening rib is secured to the back face of each slat and extends along the entire length of the slat between the overlaps and into the slots at each support, and the rib carries a stiffening bar along substantially its entire outer edge.

7. The combination of claim 6 in which the front faces of the slats have bolted-on wear plates.

8. A conveyor slat unit having an elongated slat body and connector supports bolted on to each end, each sup- CII port overlapping the slat end to which it is attached and being slotted longitudinally of the slat at the inner end of the overlap, only a single strengthening rib is secured to the back face of each slat and extends along the entire length of the slat between the overlaps and into the slots at each support, and the rib carries a stiening bar along substantially its entire outer edge.

9. The combination of claim 8 in which the strengthening rib and stiffener bar are both welded in place, and the ends of the slat are bolted to the supports by pairs of bolts located within the overlap area, each pair being spaced longitudinally of the slat adjacent opposite ends of the overlap.

l0. In an apparatus for tumbling massive work pieces in a trough-shaped conveyor enclosed in a housing having a loading and unloading doorway, and projecting a blast of abrasive particles against the work pieces to subject the tumbled work piece surfaces to the abrading action of the particles and at the same time keep the particles from leaking out through the doorway, the improvement according to which the upper portion of the doorway is in inclined position `facing upwardly and has a sliding door with a door track that extends along the inclined sides of the doorway, the door being a single rigid panel slidably tted in the track, and the conveyor is made up of metal slats each having connector supports bolted on at each end, each support overlapping the slat end to which it is attached and being slotted longitudinally of the slat at the inner end of the overlap, only a single strengthening rib is secured to the back face of each slat and extends along the entire length of the slat between the overlaps and into the slots of each support, and the rib carries a stiffening bar along substantially its entire outer edge.

References Cited in the file of this patent UNITED STATES PATENTS 2,254,219 Harnren Sept. 2, 1941 2,533,265 Keefer Dec. 12, 1950 2,716,310 Moore Aug. 30, 1955 2,918,758 Barnes Dec. 29, 1959 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Parent No., 3,048,947 August 14, 1962 Maxwell E. Fahrney et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 8, after the period, insert While FIG., 5 does not clearly show the lower roller of door 32 as riding within the trackway in the partially open position of the door, this roller rides within the trackway as better shown in FIGS. l and 2.. column line 46, for "door" read housing Signed and sealed this 3rd day of September 1963.

(SEAL) Attest: l

ERNEST w. swlDEE DAVID L- LADD Attillg Ufficer Commissioner of Patents 

